The invention relates to a method for producing a soldered connection between at least two components, in which method the components are heated in a soldering area for melting a solder, wherein the heating of the soldering area and/or the supply of solder to the soldering area is realized depending on the temperature which is determined by non-contact detection of heat radiation emitted from at least one temperature measurement zone of one of the components.
The invention further relates to an electrical plug-in connector for soldering to a coaxial cable, wherein the plug-in connector comprises a soldering area for producing a soldered connection in accordance with the above-mentioned method.
Furthermore, the invention relates to the use of such an electrical plug-in connector.
Soldered connections enable at least two components to be connected together electrically and mechanically. The components to be connected together are placed together, and subsequently a soldering area of the components is heated so that a solder arranged in the soldering area melts and wets the components in their connection area. The soldering area can be heated for example by way of an induction coil that surrounds the soldering area. In order to ensure that, on the one hand, the soldering area is heated sufficiently for the solder arranged therein to melt and wet the components and, on the other hand, excessive heating and hence potential attendant damage to the components is prevented, the application of heat is often realized depending on a temperature that is determined in a non-contact manner. For the determination of the temperature, the heat radiation emitted from at least one temperature measurement zone of one of the components is detected. The heat radiation can be detected with the aid of a pyrometer, for example.
The heat radiation emitted from the at least one temperature measurement zone depends on the emissivity of the temperature measurement zone. The emissivity of the temperature measurement zone depends, among other things, on the nature of its surface, particularly the reflectivity thereof. Surfaces with high reflectivity, in particular metal surfaces with high reflectivity, have a rather low emissivity. This low emissivity makes it difficult to determine the temperature with high process reliability and in a quickly detectable and reproducible manner.
In order to increase the emissivity of a temperature measurement zone, it has been proposed heretofore to coat the temperature measurement zone with a high-emissivity lacquer prior to the actual soldering process. However, applying a coat of lacquer has the disadvantage that the lacquer must then dry and therefore drying times must be allowed. Furthermore, when the lacquer coat is applied, solvent vapours are generated and these must be drawn away to avoid health hazards. Often, the lacquer spreads over the temperature measurement zone in an uncontrolled manner because, depending on the geometry of the temperature measurement zone, it is subject to adhesion and cohesion forces that are difficult to predict. The lacquer coating therefore often has a non-uniform thickness and hence also a non-uniform emission of heat radiation. Furthermore, sometimes the temperature measurement zone is only incompletely wetted with lacquer.
Furthermore, the use of lacquer for increasing the emissivity of the temperature measurement zone has the drawback that the lacquer may adversely affect the electrical properties of the components connected together. This applies in particular to the making of a soldered connection between electrical components which are intended to transmit high-frequency electrical signals. Here, applying a coat of lacquer to the temperature measurement zone can exacerbate passive intermodulation of the components. Passive intermodulation is understood to be the mutual interference of electrical signals that are transmitted at different frequencies via the components. Passive intermodulation is influenced, among other things, by the constituents of the lacquer that is applied to the temperature measurement zone.
As an alternative to applying a lacquer to a temperature measurement zone, it has also been proposed heretofore to adhesively bond a thin layer to the temperature measurement zone for increasing the emissivity thereof. However, such a procedure is only feasible where temperature measurement zones are readily accessible and, further, has the disadvantage that the adhesive used to adhesively bond the thin layer to the temperature measurement zone can adversely affect the electrical properties of the components, in particular the passive intermodulation performance thereof. In addition, it is known from low-frequency applications that adhesive having non-uniform thermal conductivity contributes to a further increase in measurement uncertainty.
It is therefore an object of the present invention to improve a method of the kind mentioned at the outset such that the emissivity of the at least one temperature measurement zone can be increased with high process reliability and with at most a slight adverse effect on the electrical components.